The invention relates to a tensioning device for a chain of An internal combustion engine and, more particularly, to a tensioning device, especially for an oil-pump chain, having a tensioning arm preload by a spring device and mounted in a support point.
The tensioning arm of an oil-chain of an internal combustion engine is generally arranged on a pin which is mounted in the crank case of the internal combustion engine. A spiral spring normally serves to preload the tensioning arm. The tensioning arm is supported, for example, on a rib of the crank case of the engine.
An internal combustion engine generally has other chains or belts. Thus, for example, a timing chain for the internal combustion engine is guided by a chain guide. This chain guide generally has two points of support, which are likewise supported or mounted in the crank case by way of bearing pins.
In the case of previously known tensioning devices, separate points of support were provided for each part, e.g. the tensioning arm and chain guide or other chain-supporting parts. Examples of other tensioning devices are disclosed in German Patent document 1,182,009; 1,226,850; and 4,136,003, French Patent document 1,190,167 and European Patent document EP 00 55 162 B1.
There is therefore needed a device for tensioning a chain of an internal combustion engine and a mounting for the tensioning arm of a chain which is as simple as possible and is, in particular, especially suitable for series manufacture.
These needs are met according to the present invention by a device for tensioning a chain of an internal combustion engine, especially for an oil-pump chain, having a tensioning arm preloaded by a spring device and mounted in a support point. The tensioning arm is mounted on one of the support points of a chain guide through which at least one further chain is guided.
According to the present invention, a common mounting for the tensioning arm and the chain guide is provided for at least one point of support. This means that one point of support, and the associated outlay both in material and in assembly and/or disassembly, is eliminated. Also, at least one manufacturing process step is also eliminated by the present invention.
Prior to the present invention, the respective support points or bearing pins of the tensioning arm and the chain guide on the crank case were essentially too far apart. However, it was discovered here that, particularly in the case of relatively small engines, it is possible through the use of an appropriate lengthening of one of the two parts, namely the chain guide or the tensioning arm, or, alternatively, of both parts, to combine two bearing pins or to provide a common support at just one support point or on one bearing pin.
In general, the chain guide will be lengthened in an appropriate manner towards the tensioning arm but it would, in principle, also be possible to lengthen the tensioning arm in the same way. Owing to the higher loading and the weight of the tensioning arm and the associated loading of the spiral spring, however, it will generally be the chain guide which is lengthened in an appropriate manner. However, a compromise, i.e. bringing the two close together, is also possible.
A further significant advantage of the mounting according to the present invention is realized if the chain guide, the tensioning arm, and the spiral or leaf spring interacting therewith are designed as a preassembled unit. The preassembled unit is then pushed onto the bearing pin, which can be inserted into the crank case.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.